Carton cutters and other forms of cutting instruments are used in connection with a number of activities, including box cutting, cutting of corrugated materials and packaging and a host of other tasks. U.S. Pat. No. 2,679,100 illustrates one form of knife which incorporates a two-piece housing having a cavity in which a blade is secured. The two housing sections are releasably secured to each other using a fastening screw, and the blade remains exposed in a fixed position during use. When the blade becomes dull, the user removes the fastening screw, separates the housing sections and inserts a new blade in place of the dull one. U.S. Pat. No. 2,635,337 discloses a notched linoleum cutting knife that incorporates a one-piece handle and a fixed blade. Both of these cutting devices (as well as others not specifically described herein) have exposed blades that can be hazardous and result in injury to users who are not particularly careful. For example, an unsuspecting person can be inadvertently cut by the exposed blade upon attempting to retrieve the knife from a storage container.
In addition, there are potential hazards associated with the transport of fixed-blade utility knives. Prior to transport, a user must cover the sharp edge or remove the blade to reduce the risk of harm from the blade. This can result in delays if done properly, or injury if a user simply decides to leave the blade exposed.
The dangers associated with exposed, fixed blade knives have resulted in significant improvements in the field and, in particular, in knives with a selectively retractable blade. See e.g., U.S. Pat. No. 2,862,296, U.S. Pat. No. 2,948,961, and U.S. Pat. No. 3,107,426. In such knives, the blade is disposed within the housing and is selectively extended and retracted by engaging an external member. The external member actuates a carriage which carries the blade, allowing a user to extend and retract the blade as desired.
Despite the improvements associated with cutting devices having retractable blades, there still exist other potential hazards. For example, for a knife having a retractable blade, if that blade is left exposed in an extended position, it could still result in injury. In addition to the inadvertent injuries that can potentially result from a blade left in the exposed position, other potentially more severe injuries can occur soon after a cutting stroke as applied to a box or the like is complete, when the blade is traveling at a relatively higher speed. For example, depending on the material being cut, a high drag force on the blade is often produced, causing a user to compensate by applying greater force in order to complete the cutting stroke through the material. The forces that are applied can cause the knife and the exposed blade to leave forward, that is, to accelerate beyond control just as the cut through the material is completed. At this point, the drag force is no longer present and the user holding the knife with the exposed blade cannot manually react quickly enough to stop the acceleration of the blade. This can potentially result in injuries even more severe than those sustained by virtue of a utility knife fixed in place.
Some utility knives have incorporated automatically retractable blades, such as U.S. Pat. No. 5,813,121, wherein the blade automatically retracts once pressure on the actuating button is released and the cut is completed. At the beginning of and during the cutting process using this form of cutting device, a user's thumb must remain in place on the actuating button to prevent the blade from retracting at the initiation of the cut. However, as the cutting process comes to a conclusion, a user may not be able to react quickly enough to release the actuating button, thereby potentially resulting in a similar injury discussed above.
Attempts to produce a utility knife to mitigate the aforementioned drawbacks include U.S. Pat. No. 7,356,928 (“Votolato”). Votolato discloses a cutting device having a fixed blade with a spring loaded safety guard that covers the blade. When a cut is desired, a user depresses a trigger that allows the guard to rotate and expose the blade for a single use. After the single use, the guard rotates back to a locked position, shielding the blade, regardless of whether the trigger remains depressed.
Despite addressing some of the drawbacks associated with prior art utility knives, a number of issues persist. For example, if excessive force is applied to the guard prior to depressing the trigger, the mechanism may break, thereby undesirably exposing the blade and essentially leaving a user with utility knife having a fixed blade. The same can result if the guard is damaged from dropping the knife, or the guard is worn from corrugated friction.
Another drawback in the form of a cutting instrument disclosed in Votolato is that such instruments have an inherently reduced degree of accuracy. To begin a cut at a precise point, the tip of a blade generally needs to be at least somewhat exposed so that it can manually be placed by a user at a desired location. In a cutting instrument with a blade guard like the one disclosed in Votolato, the blade is hidden, requiring a user to approximate, that is, guess at the exact location where the blade will begin to cut. This feature prevents a user from aligning the tip of the blade at a precise location, (e.g., a reference mark), thereby possibly resulting in inaccurate cuts, damage to merchandise, waste of materials and the like. In some instances, a user would be required to reposition the utility knife several times until the desired position is found.
Furthermore, using the form of cutting instruments disclosed in Votolato presents another related problem when attempting to cut with the aide of a guide. For example, in order to make a straight cut through corrugated material, a straight guide is placed precisely along a line to be cut and the side of the blade is aligned with the guide during the entire cut. This cannot be accomplished using the utility knife disclosed in Votolato because the guard would at least initially obstruct the blade from starting at the desired location beside the guide.